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Milk from Little Rock and drinking water from Philadelphia contained the highest levels of Iodine-131 from Japan yet detected by the Environmental Protection Agency, according to data released by EPA Saturday.

The Philadelphia sample is below the EPA’s maximum contaminant level (MCL) for iodine-131 in water, but the Little Rock sample is almost three times higher. However, the Food and Drug Administration observes a much higher standard for milk, and all milk samples collected so far are well below that level.

Nonetheless, the EPA does not consider the milk dangerous because the MCL is set for long-term exposure, and the iodine-131 from Japan’s Fukushima-Daichi nuclear accident is expected to be temporary and deteriorate rapidly.

The FDA’s Derived Intervention Level for iodine-131 in milk is 4700 picoCuries per liter. The EPA’s MCL for iodine-131 is 3 picoCuries per liter.

“There are a few reasons that EPA’s MCL for I-131 drinking water is different than FDA’s DIL for I-131 in any given food,” said FDA spokesman Siobhan Delancy by email. “One of them is that EPA assumes a 70 year time period for exposure, so the MCLs are basically for continual, ongoing intake. They are meant to be as low as reasonably achievable while the DILs are meant to assure that no one will reach a specific dose that would warrant protective actions as a result of an event.”

The Little Rock milk sample contained 8.9 picoCuries per liter. It was collected on March 30. On Sunday, EPA released data showing milk in Hilo, Hawaii with 24 pCi/L of cesium-134, 19 of cesium-137, and 18 of Iodine-131.

Three drinking water samples collected in Philadelphia on April 4 contained Iodine-131, according to Saturday’s data release:

A sample from the city’s Queen Lane Treatment Plant showed 2.2 picoCuries per liter—the highest concentration in EPA’s drinking water data so far.

Water collected at the Belmont Treatment Plant contained 1.3 picocuries, and

Water collected at the Baxter Treatment Plant contained 0.46 picocuries.

Philadelphia sampling sites

Philaphelphia becomes the 14th US city with radioactive fallout detected in its drinking water.

Iodine-131 has a half life of eight days: every eight days, half of its mass decays into a non-radioactive isotope of xenon.

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[Clarification: The EPA enforces a single MCL for beta emitters, which is 4mrem/year. Different concentrations of different radioisotopes reach that 4 mrem/year threshold. For example, EPA considers 3 pCi/l of Iodine-131 to be a concentration that will produce 4 mrem/year in drinking water. It considers 200 pCi/l if Cesium-137 to produce that same amount of radiation.]

Yes, David, I know. Very complicated to explain. EPA lumps beta emitters together under one collective MCL, so if you’re seeing cesium-137 in your milk or water, the MCL is 4 mrem/year; if you’re seeing iodine-131, the MCL is 4; if you’re seeing cesium-137 and iodine-131, the MCL is still 4.

Here’s a somewhat historic EPA document that speaks directly to that issue:

Although not having a 4 mrem per year equivalent level specified in the current drinking water regulations as do tritium and strontium-90, the compliance monitoring scheme indicates that an iodine-131 level of 3 pCi/L is the MCL compliance level (presumably derived from the NBS Handbook); the ANPRM indicates that 700 pCi/L is the 4 mrem/year equivalent.

UC Berkeley posted: Bay Area milk is over the Federal limit of 3 pCi/l combined for March 8: I-131 (2.7) Cs-134 (5.9) and Cs-137 (5.9) appeared for the first time. 14.5 is big news, but you wouldn’t get that from the summary. You have to convert bequerels to picocuries first. http://www.unitconversion.org/radiation-activity/becquerels-to-picocuries-conversion.html

Jeff, if gamma and beta emitters are all lumped together under the 3 pCi/L MCL, then surely EPA should be reporting an aggregate value as the important benchmark (as well as reporting the individual concentrations of each radionuclide); and not suggesting that you can consume up to 3 pCi/L of I-131 AND 3 pCi/L of Cs-137 AND 3 pCi/L of strontium?

Perhaps I have misunderstood EPA reports, but I have been reading this news very carefully, checking sources, and doing a lot of research, and had not picked up on what you’re reporting in this comment – I feel 100% confident none of my friends and family had either. So thank you very much for your research.

chargirl, I don’t know that EPA has such a definition, but let me go at your question by trying to define long-term.

The MCL is established for something like a steady level of contamination in a constant water source that’s serving a community over time. And EPA has been anticipating that these Fukushima emissions will be short-lived (though we’ve not yet seen the end of it):

While the levels in the rainwater exceed the applicable Maximum Contaminant Level (MCL) of 3piC/L for drinking water, it is important to note that the corresponding MCL for iodine-131 was calculated based on long-term chronic exposures over the course of a lifetime 70 years. The levels seen in rainwater are expected to be relatively short in duration.

However, I’m not sure how reliable that 70-years statement really is as a definition of long-term. Because the EPA has another MCL that it takes more seriously, and that is, that people should not be exposed to more than 4 millirem per year. To make sense of that number we need to be able to express picocuries as millirems, but that’s what that legacy document does that I quoted above:

“the compliance monitoring scheme indicates that an iodine-131 level of 3 pCi/L is the MCL compliance level; the ANPRM indicates that 700 pCi/L is the 4 mrem/year equivalent.”

What this all means to me is that if you’re a water company, EPA will insist you keep the gamma/beta emitters in your water below 3 pCi/L in pursuit of another aim, which is to keep your customers’ annual radiation exposure below 700, or, put another way, below 4mrem, over the course of a year.

If we should not be exposed to more than 700 pCi/L per year, then anyone who drinks two liters of Boise rainwater or 13 liters of Hilo milk is in trouble. Both those scenarios may be unlikely, but they’re beginning to get closer to likely than the reassurances we’ve been receiving would seem to indicate.